Carbon strand radio frequency heating susceptor

ABSTRACT

A method for heating materials by application of radio frequency (“RF”) energy is disclosed. For example, the disclosure concerns a method and apparatus for RF heating of petroleum ore, such as bitumen, oil sands, oil shale, tar sands, or heavy oil. Petroleum ore is mixed with a substance comprising mini-dipole susceptors such as carbon strands. A source is provided which applies RF energy to the mixture of a power and frequency sufficient to heat the mini-dipole susceptors. The RF energy is applied for a sufficient time to allow the mini-dipole susceptors to heat the mixture to an average temperature greater than about 212° F. (100° C.). Optionally, the mini-dipole susceptors can be removed after the desired average temperature has been achieved. The susceptors may provide advantages for the RF heating of hydrocarbons, such as higher temperatures (sufficient for distillation or pyrolysis), anhydrous processing, and greater speed or efficiency.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

CROSS REFERENCE TO RELATED APPLICATIONS

This specification is related to McAndrews, Held & Malloy attorneydocket numbers:

-   -   20476US01    -   20478US01    -   20480US01    -   20481US01    -   20484US01    -   20485US01    -   20486US01    -   20487US01    -   20496US01        filed on or about the same date as this specification, each of        which is incorporated by reference here.

BACKGROUND OF THE INVENTION

The disclosure concerns a method and apparatus for heating materials byapplication of radio frequency (“RF”) energy, also known aselectromagnetic energy. In particular, the disclosure-concerns anadvantageous method for RF heating of materials with a low or zeroelectric dissipation factor, magnetic dissipation factor, and electricalconductivity, such as petroleum ore. For example, the disclosure enablesefficient, low-cost heating of bituminous ore, oil sands, oil shale, tarsands, or heavy oil.

Bituminous ore, oil sands, tar sands, and heavy oil are typically foundas naturally occurring mixtures of sand or clay and dense and viscouspetroleum. Recently, due to depletion of the world's oil reserves,higher oil prices, and increases in demand, efforts have been made toextract and refine these types of petroleum ore as an alternativepetroleum source. Because of the extremely high viscosity of bituminousore, oil sands, oil shale, tar sands, and heavy oil, however, thedrilling and refinement methods used in extracting standard crude oilare typically not available. Therefore, bituminous ore, oil sands, oilshale, tar sands, and heavy oil are typically extracted by strip mining,or in situ techniques are used to reduce the viscosity by injectingsteam or solvents in a well so that the material can be pumped. Undereither approach, however, the material extracted from these deposits canbe a viscous, solid or semisolid form that does not easily flow atnormal oil pipeline temperatures, making it difficult to transport tomarket and expensive to process into gasoline, diesel fuel, and otherproducts. Typically, the material is prepared for transport by addinghot water and caustic soda (NaOH) to the sand, which produces a slurrythat can be piped to the extraction plant, where it is agitated andcrude bitumen oil froth is skimmed from the top. In addition, thematerial is typically processed with heat to separate oil sands, oilshale, tar sands, or heavy oil into more viscous bitumen crude oil, andto distill, crack, or refine the bitumen crude oil into usable petroleumproducts.

The conventional methods of heating bituminous ore, oil sands, tarsands, and heavy oil suffer from numerous drawbacks. For example, theconventional methods typically utilize large amounts of water, and alsolarge amounts of energy. Moreover, using conventional methods, it hasbeen difficult to achieve uniform and rapid heating, which has limitedsuccessful processing of bituminous ore, oil sands, oil shale, tarsands, and heavy oil. It can be desirable, both for environmentalreasons and efficiency/cost reasons to reduce or eliminate the amount ofwater used in processing bituminous ore, oil sands, oil shale, tarsands, and heavy oil, and also provide a method of heating that isefficient and environmentally friendly, which is suitable forpost-excavation processing of the bitumen, oil sands, oil shale, tarsands, and heavy oil.

One potential alternative heating method is RF heating. “RF” is mostbroadly defined here to include any portion of the electromagneticspectrum having a longer wavelength than visible light. Wikipediaprovides a definition of “radio frequency” as comprehending the range offrom 3 Hz to 300 GHz, and defines the following sub ranges offrequencies:

Name Symbol Frequency Wavelength Extremely low ELF 3-30 Hz10,000-100,000 km frequency Super low frequency SLF 30-300 Hz1,000-10,000 km Ultra low frequency ULF 300-3000 Hz 100-1,000 km Verylow frequency VLF 3-30 kHz 10-100 km Low frequency LF 30-300 kHz 1-10 kmMedium frequency MF 300-3000 kHz 100-1000 m High frequency HF 3-30 mHz10-100 m Very high frequency VHF 30-300 mHz 1-10 m Ultra high frequencyUHF 300-3000 mHz 10-100 cm Super high SHF 3-30 GHz 1-10 cm frequencyExtremely high EHF 30-300 GHz 1-10 mm frequency

“RF heating,” then, is most broadly defined here as the heating of amaterial, substance, or mixture by exposure to RF energy. For example,microwave ovens are a well-known example of RF heating. RF heating canhave advantages of high speed, deep or adjustable heating depth, or evenselective heating where one component of a mixture receives more heatthan another. For instance, RF energy may penetrate wood fibers to cureinternal adhesives without scorching. In some petroleum processesboiling water is added to relatively cold petroleum ores and thetemperature of the resulting mixture/slurry may be insufficient. As itcan be expensive to raise the temperature of water above the boilingpoint at atmospheric pressure RF heating techniques can increase slurryheat without steam or pressure vessels.

The nature and suitability of RF heating depends on several factors. Ingeneral, most materials accept electromagnetic waves, but the degree towhich RF heating occurs varies widely. RF heating is dependent on thefrequency of the electromagnetic energy, intensity of theelectromagnetic energy, proximity to the source of the electromagneticenergy, and type of RF energy fields. RF heating material propertiesinclude conductivity of the material to be heated, whether the materialto be heated is magnetic or non-magnetic, and the dielectricpolarizability. Pure hydrocarbon molecules are substantiallynonconductive, of low dielectric loss factor and nearly zero magneticmoment. Thus, pure hydrocarbon molecules themselves are only fairsusceptors for RF heating, e.g. they may heat only slowly in thepresence of RF fields. For example, the dissipation factor D of aviationgasoline may be 0.0001 and distilled water 0.157 at 3 GHz, such that RFfields apply heat 1570 times faster to the water in emulsion to oil.

Similarly, a water/hydrocarbon mixture may not achieve desirable RFheating. Water, even distilled water, can be a susceptor for RF heating.However, the use of water in RF heating is limited to 212° F. (100° C.)at atmospheric pressures, as the vapor phase of water (steam) is a poorRF susceptor. Moreover, in some regions, water resources may beinsufficient, and it may be limiting or even impractical to processpetroleum ores with hot water or steam.

SUMMARY OF THE INVENTION

An aspect of the present invention is a method and apparatus for RFheating of materials with a low or zero electric dissipation factor,magnetic dissipation factor, and electrical conductivity. For example,the present invention may be used for RF heating of petroleum ore, suchas bituminous ore, oil sands, tar sands, oil shale, or heavy oil. Thepresent invention is especially suited for RF heating of petroleum oreabove 100° C., where liquid water cannot exist at ordinary atmosphericpressure. An exemplary embodiment of the present method comprises firstmixing about 10% to about 99% by volume of a substance such as petroleumore with about 1% to about 50% by volume of a substance comprisingmini-dipole susceptors. The mixture is then subjected to a radiofrequency in a manner which creates heating of the mini-dipolesusceptors. The radio frequency can be applied for a sufficient time toallow the min-dipole susceptors to heat the surrounding substancethrough conduction, so that the average temperature of the mixture canbe greater than about 212° F. (100° C.). After the mixture has achievedthe desired temperature, the radio frequency can be discontinued, andsubstantially all of the mini-dipole susceptors can optionally beremoved, resulting in a heated substance that can be substantially freeof the mini-dipole susceptors used in the RF heating process.

Other aspects of the invention will be apparent from this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram depicting a process and equipment for RFheating of a petroleum ore using mini-dipole susceptors.

FIG. 2 illustrates mini-dipole and related susceptor structuresdistributed in a petroleum ore (not to scale), with associated RFequipment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The subject matter of this disclosure will now be described more fully,and one or more embodiments of the invention are shown. This inventionmay, however, be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are examples of the invention, which has the full scopeindicated by the language of the claims.

In an exemplary method, a method for heating a petroleum ore such asbituminous ore, oil sands, tar sands, oil shale, or heavy oil using RFenergy is provided.

Petroleum Ore

The presently disclosed method can be utilized to either heat apetroleum ore that has been extracted from the earth, prior todistillation, cracking, or separation processing, or can be used as partof a distillation, cracking, or separation process. The petroleum orecan comprise, for example, bituminous ore, oil sands, tar sands, oilshale, or heavy oil that has been extracted via strip-mining ordrilling. If the extracted petroleum ore is a solid or includes solidswith a volume greater than about 1 cubic centimeter, the petroleum orecan be crushed, ground, or milled to a slurry, powder, orsmall-particulate state prior to RF heating. The petroleum ore cancomprise water, but alternatively contains less than 10%, less than 5%,or less than 1% by volume of water. Most preferably, the petroleum orecan be substantially free of added water, as the present inventionprovides a means of RF heating without the presence of any water. Thisdisclosure is especially suitable for RF heating of hydrocarbons withoutwater emulsion, and for RF heating above 100° C. where liquid water maynot be available as an emulsified susceptor without a pressure vessel.

The petroleum ore used in the present method is typically non-magneticor low-magnetic, and non-conductive or low-conductive. Therefore, thepetroleum ore alone is not generally suitable for rapid RF heating. Forexample, exemplary petroleum ore when dry, e.g. free from water, mayhave a dielectric dissipation factor (ε″) less than about 0.01, 0.001,or 0.0001 at 3000 MHz. Exemplary petroleum ore may also have anegligible magnetic dissipation factor (μ″), and the exemplary petroleumore may also have an electrical conductivity of less than 0.01, 0.001,or 0.0001 S·m⁻¹ at 20° C. The presently disclosed methods, however, arenot limited to petroleum products with any specific magnetic orconductive properties, and can be useful to RF heat substances with ahigher dielectric dissipation factors (ε″), magnetic dissipation factor(μ″), or electrical conductivity. The presently disclosed methods arealso not limited to petroleum ore, but are widely applicable to RFheating of any substance that has dielectric dissipation factor (ε″)less than about 0.05, 0.01, or 0.001 at 3000 MHz. It is also applicableto RF heating of any substance that has an electrical conductivity ofless than 0.01 S·m⁻¹, 1×10⁻⁴ S·m⁻¹, or 1×10⁻⁶ S·m⁻¹ at 20° C.

Susceptor Mini-Dipoles

The presently disclosed method utilizes a mini-dipole antenna susceptorstructure in conjunction with the petroleum ore to provide improved RFheating. A “susceptor” is herein defined as any material which absorbselectromagnetic energy and transforms it to heat. A “mini-dipole”susceptor is herein defined as any susceptor that reacts as a dipoleantenna to RF energy, and which has a longest dimension less than 10 cm,5 cm, 1 cm, or 0.5 cm.

Susceptors have been suggested for applications such as microwave foodpacking, thin-films, thermosetting adhesives, RF-absorbing polymers, andheat-shrinkable tubing. Examples of susceptor materials are disclosed inU.S. Pat. Nos. 5,378,879; 6,649,888; 6,045,648; 6,348,679; and4,892,782, which are incorporated by reference herein.

In the presently disclosed method, thin filament-like conductivestructures, such as fine metal wires or carbon fibers can be distributedthrough the hydrocarbon ore as susceptors. The filaments formmini-dipole antennas to capture the incident RF energy/electromagneticfields and to dissipate them as heat. The method of heating can beresistive by the motion of electrons or charge carriers through theresistance of the dipole structure, e.g. electric current I and heatingaccording to Joule's First law or Q=I²Rt.

In general, antennas can comprise conductive structures used totransduce electric currents in electromagnetic waves and vice versa. Thecanonical antennas are the line and circle, corresponding to the dipoleand the loop types, and the curl and divergence of electric current. Thefield regions of the simplest antennas include reactive near field,middle field, and radiated far field regions. The field typessurrounding antennas include both electric (E) fields and magnetic (H)fields. When in conductive media electric currents may exist about theantenna, e.g. antennas may have aspects of being electrodes as well. AnRF applicator may be interchangeably referred to as a dipole antenna(such as a skeleton slot antenna) or an electrode pair.

A half wave dipole antenna comprises a thin line-like conductor near onehalf wavelength in length (I=λ/2). The effective aperture or capturearea of a loaded resistively matched small dipole antenna can beA_(em)=3λ²/16π=0.06λ², and if the dipole antenna comprises a thinconductor the effective width may about 1000 times larger than thephysical width. Thus, a single thin wire dipole antenna can transduce RFenergy from a very large surrounding area relative its physical area.For example, thin metallic foil strips have been sown as radar chaff andthe reflection area was much greater than the physical area of the smalldipoles. An example of dipole aperture area was the orbiting dipole beltrealized about the earth in Project West Ford (“Measured PhysicalCharacteristics Of The West Ford Belt”, Heart F. E. et. al., Proceedingsof the IEEE, Vol. 52, Issue 5, May 1964 pages 519-533). In project WestFord, a sparsely sown dipole cloud (dipole wires 0.0018 cm diameter,e.g. AWG 53, and 1.78 cm length) about the earth was useful for thepassive relay of communications (˜8 GHz) between ground stations. Thedipole formation was akin perhaps to forming rings around the earth,similar to the rings of Saturn, yet the dipole formation was opticallytransparent. Even a small number of thin dipoles can have great effectin RF applications.

Here, mini-dipole filaments may be provided at a resonant length, suchas ½ wavelength. In other instances the mini-dipole may be electricallysmall and below resonance to increase the depth of penetration of RFfields. For example, the mini-dipole may be ¼ wavelength, ⅛ wavelength,or 1/16 wavelength. For ½ wave resonant operation, the resistance of theconductive fibers may preferentially be about 73 Ohms to provide aresistive load for the dipole they form, e.g. the radiation resistanceR_(r) is about equal to the dipole conductor loss resistance R_(I).Alternatively, the resistance of the conductive fibers may from 50 to 73Ohms, or from 73 Ohms to 100 Ohms.

RF energy may be applied at a single frequency or a range or frequenciesfor different heating effects. For instance, deep heating maysimultaneously occur with increased surface heating by application of alow and high RF frequency simultaneously. The surface heating mayprovide a surface hardening, drying effect, appearance change orotherwise. The mini-dipole susceptors 210 have enhanced susception, e.g.increased RF heating, at harmonic frequency intervals, especially oddharmonics (for example, F, 3F, and 5F), where F is the fundamentalresonance frequency). Increased thermal gradient with increasedfrequency occurs with mini-dipole susceptors. The 3 dB (50 percentheating change) bandwidth of thin ½ wave dipoles of approximatelyfundamental resonance can be about 13 percent for small diameters, e.g.d<λ/50.

Mini-dipole RF heating can be performed, for example, using carbonfiber, carbon fiber floc, or carbon fiber cloth (e.g., carbon fibersquares) susceptors. Carbon fibers or carbon fiber floc may be less than5 cm long and less than 0.5 mm in diameter. Preferably, carbon fibers orcarbon fiber floc are less than 1 cm long or less than 0.1 mm indiameter. Carbon fiber cloth dipoles or carbon fiber squares can be forexample less than 5 cm by 5 cm by 0.5 mm, alternatively less than 1 cmby 1 cm by 0.5 mm. The mini dipole susceptor fibers do not need to bestraight and it can be unimportant whether they are in contact with onanother.

Suitable carbon fibers, such as the present generation of graphitestructural fibers, preferably provide circuit resistance, e.g conductorloss. Graphite fibers are also low in cost and may be relativelychemically inert. The fibers may be about 0.02 mm, 0.010 mm, 0.005 mm,or 0.001 mm in diameter and may comprise carbon atoms bonded together inmicroscopic crystals that are approximately aligned parallel to the longaxis of the fiber. A commercial example graphite fiber is HexTow 1900/IMChopped Carbon Fiber by Hexcell Corporation of Stamford Connecticut. Theproduct is vended as rectangular flakes that break apart releasing theindividual fibers during processing, forming a method for the release ofthe carbon fiber dipoles into the hydrocarbon ore.

Suitable carbon fiber square susceptors may be related to both thedipole and the loop form of antennas. When the circumference of thesquare approaches ½ wavelength in the media the resistive squareapproximates the panel form of the loop antenna and electrical currentis transduced to flow circumferentially around the perimeter of thesquare, e.g. electromagnetic curl. While not isotropic, the radiationpattern of a ½ wavelength perimeter square loop antenna may have shallowpattern nulls, and the square of course has a larger physical surfacearea than the thin filamentary dipole and may be preferential for higherrates of heat application.

Mixing of Petroleum Ore and Susceptor Dipoles

Preferably, a mixing or dispersion step is provided, whereby acomposition comprising the susceptor dipoles is mixed or dispersed inthe petroleum ore. The mixing step can occur after the petroleum ore hasbeen crushed, ground, or milled, or in conjunction with the crushing,grinding, or milling of the petroleum ore. The mixing step can beconducted using any suitable method or apparatus that disperses thesusceptor dipoles in a substantially uniform manner. For example, a sandmill, cement mixer, continuous soil mixer, or similar equipment can beused. The susceptor dipoles may also be mixed or further mixed duringtransport in a pipeline.

An advantageous capability of the presently disclosed methods can be thefact that large amounts of susceptors can optionally be used withoutnegatively affecting the chemical or material properties of theprocessed petroleum ore, because the susceptor particles may be removed.Therefore, a composition comprising susceptors can for example be mixedwith the petroleum ore in amount from about 1% to about 50% by volume ofthe total mixture. Alternatively, the composition comprising susceptorscomprises from about 1% to about 25% by volume of the total mixture, orabout 1% to about 10% by volume of the total mixture.

The susceptors can be distributed uniformly in the material to beheated, as when uniform heating is contemplated. Alternatively, thesusceptors can be non-uniformly distributed if non-uniform heating iscontemplated. The electromagnetic capture area of a ½ wavelengthresistive dipole antenna in, for example, air at 2450 MHz is0.119λ²/2=1.4 square inches (3.6 square cm), which would correspond to alength of the dipole of 2.4 inches (6.1 cm). The application rate(density of the susceptors) for this example may be about 1 susceptorper cubic inch of material to be heated (or 0.5 per cubic cm). In othermaterials, and for resonance, the susceptor dipole length may beI=(λ/2)(1/√μ_(r)ε_(r)). Depending on the material or frequency, averagesusceptor density may be from 0.1 susceptor per cubic cm to about 10susceptors per cubic cm, or 1 susceptor per cubic cm to about 5susceptors per cubic cm. When the susceptors are closer than about λ/2π,however, significant near field coupling occurs between dipoles andadditional susceptor density may not be further beneficial.

The exemplary mini-dipole susceptors are distinguishable from merelyusing carbon as a susceptor material, because the RF heating is notgenerated primarily by dielectric heating or magnetic moment heating duethe atomic or molecular properties of the carbon, but rather, isgenerated due to the electrically conductive nature of the carbon fiber,carbon fiber floc, or cloth and its shape as an antenna structure, e.g.a dipole or dipole antenna array is formed in situ the media to beheated.

Radio Frequency Heating

After the susceptor particle composition has been mixed in the petroleumore, the mixture can be heated using RF energy. An RF source can beprovided which applies RF energy to cause the susceptors to generateheat. The resistive heat generated inside the susceptors causes theoverall mixture to heat by conduction. The preferred RF frequency,power, and source proximity vary in different embodiments depending onthe properties of the petroleum ore, the susceptor particle selected,and the desired mode of RF heating.

In one exemplary embodiment, RF energy can be applied in a manner thatcauses the susceptors to heat by near fields, e.g. induction. Inductionheating involves applying a near field RF field to electricallyconducting materials to create current flow thereon. An eddy current iscreated when an electrically conducting material is exposed to achanging magnetic field due to relative motion of the field source andconductor; or due to variations of the field with time. This can cause acirculating flow or current of electrons within the conductor. Thesecirculating eddies of current create electromagnets with magnetic fieldsthat opposes the change of the magnetic field according to Lenz's law.These eddy currents generate heat. The degree of heat generated in turn,depends on the strength of the RF field, the electrical conductivity ofthe heated material, and the change rate of the RF field. There can bealso a relationship between the frequency of the RF field and the depthto which it penetrate the material; in general, higher RF frequenciesgenerate a higher heat rate.

The RF source used for induction RF heating can be for example a loopantenna or magnetic near-field applicator suitable for generation of amagnetic field. The RF source typically comprises an electromagnetthrough which a high-frequency alternating current (AC) is passed. Forexample, the RF source can comprise an induction heating coil, a chamberor container containing a loop antenna, or a magnetic near-fieldapplicator. The exemplary RF frequency for induction RF heating can befrom about 50 Hz to about 3 GHz. Alternatively, the RF frequency can befrom about 10 kHz to about 10 MHz, 10 MHz to about 100 MHZ, or 100 MHzto about 2.5 GHz. The power of the RF energy, as radiated from the RFsource, can be for example from about 100 KW to about 2.5 MW,alternatively from about 500 KW to about 1 MW, and alternatively, about1 MW to about 2.5 MW. It can be preferable to properly thermally loadthe mini-dipole susceptors, as even a single fine strand can transducelarge amounts of energy.

In yet another embodiment, the RF energy source used can be far-field RFenergy, and the susceptors selected act as mini-dipole antennas thatgenerate heat. One property of a dipole antenna is that it can convertRF waves to electrical current. The material of the dipole antenna,therefore, can be selected such that it resistively heats under anelectrical current. A far-field RF energy, e.g. a radio wave, ratherthan a near-field or induction field, can be applied to the mixture tobe heated. The RF frequency used can be for example the resonantfrequency of the carbon-fiber dipoles. Heating penetration can also beadjusted by varying the dipole size or the frequency away fromresonance. The power of the RF energy radiated from the applicator canbe adjusted over a wide range as the dipole susceptor is a passivelinear device. RF heat application rates may be for example 100 wattsper cubic foot of to about 10 KW per cubic foot. As background, thepaper “The RF Characteristics Of Thin Dipoles, C. L. Mack and B.Reiffen, Proceedings of the Institute of Electrical and ElectronicsEngineers (IEEE), Volume 52, Issue 5, May 1964, pp 533-542 isincorporated herein as a reference in its entirety.

In each of the presently exemplary embodiments, RF energy can be appliedfor a sufficient time to allow the heated susceptor mini-dipoles to heatthe surrounding hydrocarbon oil, ore, or sand. For example, RF energycan be applied for sufficient time so that the average temperature ofthe mixture can be greater than about 150° F. (70° C.). Alternatively,RF energy can be applied until the average temperature of the mixture isabove that of boiling water for example, greater than 212° F. (100° C.),or greater than 200° F. (90° C.), 300° F. (150° C.), or 400° F. (200°C.). Alternatively, RF energy can be applied until the averagetemperature of the mixture is, for example, sufficient for distillationor pyrolysis according to the molecular weight of the hydrocarbon.Temperatures in excess of 1000° F. (540° C.) are possible depending onthe dipole fiber material, e.g. temperatures above those typical orneeded for hydrocarbon processing may be achieved. In a variation on theexemplary embodiment, the RF energy can be applied as part of adistillation or cracking process, whereby the mixture can be heatedabove the pyrolysis temperature of the hydrocarbon in order to breakcomplex molecules such as kerogens or heavy hydrocarbons into simplermolecules (e.g. light hydrocarbons). It is presently believed that thesuitable length of time for application of RF energy in the presentlydisclosed embodiments can be preferably from about 15 seconds, 30seconds, or 1 minute to about 10 minutes, 30 minutes, or 1 hour. Afterthe hydrocarbon/susceptor mixture has achieved the desired averagetemperature, exposure of the mixture to the radio frequency can bediscontinued. For example, the RF source can be turned off or halted, orthe mixture can be removed from the RF source.

Removal/Reuse of Susceptors

In certain embodiments, the present disclosure also contemplates theability to remove the susceptors after the hydrocarbon/susceptor mixturehas achieved the desired average temperature.

If the susceptors are left in the mixture, in certain embodiments thismay undesirably alter the chemical and material properties of theprimary substance. For example, it can be undesirable for a compositionto contain significant amounts of metal or metal oxide powders, polymerdipoles, or fibers. One alternative is to use a low volume fraction ofsusceptor, if any. For example, U.S. Pat. No. 5,378,879 describes theuse of permanent susceptors in finished articles, such asheat-shrinkable tubing, thermosetting adhesives, and gels, and statesthat articles loaded with particle percentages above 15% are generallynot preferred, and in fact, are achievable in the context of that patentonly by using susceptors having relatively lower aspect ratios. Thepresent disclosure provides the alternative of removing the susceptorsafter RF heating. By providing the option of removing the susceptorsafter RF heating, the present disclosure can reduce or eliminateundesirable altering of the chemical or material properties of thepetroleum ore, while allowing a large volume fraction of susceptors tobe used. The susceptor particle composition can thus function as atemporary heating substance, as opposed to a permanent additive.

Removal of the susceptor particle composition can vary depending on thetype of susceptors used and the consistency, viscosity, or averageparticle size of the mixture. If necessary or desirable, removal of thesusceptors can be performed in conjunction with an additional mixingstep. If a magnetic or conductive susceptor is used, substantially allof the susceptors can be removed with one or more magnets, such asquiescent or direct-current magnets. Carbon fiber, carbon floc, orcarbon fiber cloth susceptors can be removed through flotation,centrifuging, or filtering. For example, removal of the susceptors canbe performed either while the petroleum ore/susceptor mixture is stillbeing RF heated, or within a sufficient time after RF heating has beenstopped so that the temperature of the petroleum ore decreases by nomore than 30%, and alternatively, no more than 10%. For example, thepetroleum ore can maintain an average temperature of greater than 200°F. (93° C.) during any removal of the susceptors, alternatively anaverage temperature of greater than 400° F. (200° C.).

Another advantage of the exemplary embodiments of the present disclosurecan be that the susceptors can optionally be reused after they areremoved from a heated mixture.

Alternatively, in certain instances it may be appropriate to leave someor all of the susceptors in some or all of the material of the mixtureafter processing. For example, if the susceptors are elemental carbon,which is non-hazardous and inexpensive, it may be useful to leave thesusceptors in the mixture after heating, to avoid the cost of removal.For another example, a petroleum ore with added susceptor material canbe pyrolyzed to drive off useful lighter fractions of petroleum, whichare collected in vapor form essentially free of the susceptor material,while the bottoms remaining after pyrolysis may contain the susceptorand be used or disposed of without removing the susceptor.

Referring to FIG. 1, a flow diagram of an embodiment of the presentdisclosure is provided. A container 1 is included, which contains afirst substance with a dielectric dissipation factor, epsilon, less than0.05 at 3000 MHz. The first substance, for example, may comprise apetroleum ore, such as bituminous ore, oil sand, tar sand, oil shale, orheavy oil. A container 2 contains a second substance comprisingmini-dipole susceptors. The mini-dipole susceptors may comprise any ofthe mini-dipoles discussed herein, such as carbon fibers, carbon fiberfloc, or carbon cloth. A mixer 3 is provided for dispersing the secondmini-dipole susceptor substance into the first substance. The mixer 3may comprise any suitable mixer for mixing viscous substances, soil, orpetroleum ore, such as a sand mill, soil mixer, or the like. The mixermay be separate from container 1 or container 2, or the mixer may bepart of container 1 or container 2. A heating vessel 4 is also providedfor containing a mixture of the first substance and the second substanceduring heating. The heating vessel may also be separate from the mixer3, container 1, and container 2, or it may be part of any or all ofthose components. Further, an antenna 5 is provided, which is capable ofemitting electromagnetic energy as described herein to heat the mixture.The antenna 5 may be a separate component positioned above, below, oradjacent to the heating vessel 4, or it may comprise part of the heatingvessel 4. Optionally, a further component, filter 6 may be provided,which is capable of filtering substantially all of the second substancecomprising mini-dipoles from the first substance. Tailings 7 may then beremoved or disposed of after filtration, while a heated petroleumproduct 8 may be stored or transported.

Referring to FIG. 2, an apparatus for RF heating petroleum ore isdescribed. Mini-dipoles 210 are distributed in petroleum ore 220. Themini-dipoles may preferentially be formed of partially conductive carbonfibers. Fabric sections 212 may contain the carbon fibers ofmini-dipoles 210, becoming unraveled to release the carbon fibermini-dipoles. In another instance the fabric sections 212 may remainintact forming mini-loop antenna susceptors 214. The preferred carbonfibers may in practice comprise a variety of geometric forms whileproviding RF susceptance, antenna functionality, heat application tohydrocarbon ore 220. The petroleum ore 220 may contain any concentrationof hydrocarbon molecules, which themselves may not be suitablesusceptors for RF heating. An antenna 230 is placed in sufficientproximity to the mixture of mini-dipoles 210 and petroleum ore 220 tocause heating therein, which may be near field or far field or both. Theantenna 230 may be a bowtie dipole although the invention is not solimited, and any form for antenna may be suitable depending on thetrades. A vessel 240 may be employed, which may take the form of a tank,a separation cone, or even a pipeline. A method stirring the mix may beemployed, such as a pump (not shown). Vessel 240 may be omitted in someapplications, such as heating dry ore on a conveyor. RF shielding 250can be employed as is common. Transmitting equipment 260 produces thetime harmonic, e.g. RF, current for antenna 230. The transmittingequipment 260 may contain the various RF transmitting equipment featuressuch as impedance matching equipment (not shown), variable RF couplers(not shown), and control systems (not shown).

Thus, enhanced RF heating of petroleum ores and hydrocarbons is providedby adding electrically conductive structures therein, such as thincarbon fibers or squares with sufficient electrical resistance. Theconductive structures may provide antenna like properties, responding toelectromagnetic fields and radio waves with electrical current flowthereupon for heating. A relatively small number or conductivestructures may be sufficient as the effective aperture of a thin antennacan be much larger than its physical area.

EXAMPLES

The following examples illustrate several of the exemplary embodimentsof the present disclosure. The examples are provided as small-scalelaboratory confirmation examples. However, one of ordinary skill in theart will appreciate, based on the foregoing detailed description, how toconduct the following exemplary methods on an industrial scale.

Example 1 RF Heating of Petroleum Ore Without Susceptor Addition

A sample of ¼ cup of Athabasca oil sand was obtained at an averagetemperature of 72° F. (22° C.). The sample was contained in a Pyrexglass container. A GE DE68-0307A microwave oven was used to heat thesample at 1 KW at 2450 MHz for 30 seconds (100% power for the microwaveoven). The resulting average temperature after heating was 125° F. (51°C).

Example 2 RF Heating of Petroleum Ore With The Addition Of Carbon FiberSusceptors

A sample of ¼ cup of Athabasca oil sand was obtained at an averagetemperature of 72° F. (22° C.). The sample was contained in a Pyrexglass container. 1 Tablespoon of carbon fiber floc (HexTow 1900/IMChopped Carbon Fiber by Hexcell Corporation of Stamford Connecticut) atan average temperature of 72° F. (22° C.) was added to the Athabasca oilsand and uniformly mixed. A GE DE68-0307A microwave oven was used toheat the mixture at 2450 MHz for 30 seconds. The resulting averagetemperature of the mixture after heating was 240° F. (115° C.).

Example 3 RF Heating of Petroleum Ore With Carbon Fiber SquareSusceptors

A sample of ¼ cup of Athabasca oil sand was obtained at an averagetemperature of 72° F. (22° C.). The sample was contained in a Pyrexglass container. 1 Tablespoon of carbon fiber squares at an averagetemperature of 72° F. (22° C.) was added to the Athabasca oil sand anduniformly mixed. A GE DE68-0307A microwave oven was used to heat themixture at 1 KW at 2450 MHz. The resulting average temperature of themixture after heating was 180° F. (82° C.).

1. A method for heating a petroleum ore comprising the steps of: (a)providing a mixture of about 10% to about 99% by volume of a petroleumore and about 1% to about 50% by volume of a composition comprisingmini-dipole susceptors; (b) applying to the mixture radio frequencyenergy of a power and frequency sufficient to heat the mini-dipolesusceptors; and; (c) continuing to apply the radio frequency energy fora sufficient time to allow the mini-dipole susceptors to heat themixture to an average temperature greater than about 212° F. (100° C.).2. The method of claim 1, further comprising removing the mini-dipolesusceptors from the petroleum ore.
 3. The method of claim 1, wherein themini-dipole susceptors are carbon fibers, carbon fiber floc, or carbonfiber cloth.
 4. The method of claim 4, further comprising subsequentlyremoving the mini-dipole susceptors from the petroleum ore.
 5. Themethod of claim 1, wherein the petroleum ore comprises bituminous ore,oil sand, tar sand, oil shale, or heavy oil.
 6. The method of claim 1,wherein the average size of the mini-dipole susceptors is less than 1cubic cm.
 7. The method of claim 10, wherein the average size of themini-dipole susceptors is less than 1 cubic mm.
 8. The method of claim1, wherein the radio frequency is from 10 kHz to 10 MHz.
 9. The methodof claim 1, wherein the radio frequency is from 100 MHz to 3 GHz. 10.The method of claim 1, wherein the mixture of step (a) comprises fromabout 70% to about 90% by weight of petroleum ore and from about 30% toabout 10% by weight of mini-dipole susceptors.
 11. The method of claim1, wherein the mixture is heated to above 400° F. (200° C.).
 12. Themethod of claim 1, wherein the mixture includes less than about 5% byvolume of water.
 13. The method of claim 1, wherein the mixture includesless than about 1% by volume of water.
 14. The method of claim 1,wherein the mixture comprises a powder, granular substance, slurry, orviscous liquid.
 15. A method for RF heating comprising: (a) providing afirst substance with a dielectric dissipation factor, epsilon, less than0.05 at 3000 MHz; (b) adding a second substance comprising mini-dipolesusceptors with an average volume of less than 1 cubic cm to create adispersed mixture, wherein the second substance comprises between about1% to about 40% by volume of the mixture; (c) applying a radio frequencyto the mixture at a power level and frequency sufficient to heat themini-dipole susceptors; (d) maintaining the radio frequency for asufficient time to allow the mini-dipole susceptors to heat the mixtureto an average temperature of greater than 212° F. (100° C.); and (e)removing the mini-dipole susceptors from the mixture.
 16. The method ofclaim 18, wherein the mixture comprises a powder, granular substance,slurry, or viscous liquid.
 17. The method of claim 18, wherein themini-dipole susceptors are removed by filtering or floating themini-dipole susceptors.
 18. A composition suitable for RF heatingcomprising a first substance that is a petroleum ore with a dielectricdissipation factor, epsilon, less than 0.05 at 3000 MHz, and a secondsubstance comprising mini-dipole susceptors that are carbon fibers,carbon fiber floc, or carbon fiber cloth.
 19. A system for RF heatingcomprising: (a) a container comprising a first substance with adielectric dissipation factor, epsilon, less than 0.05 at 3000 MHz, (b)a container comprising a second substance comprising mini-dipolesusceptors; (c) a mixer for dispersing the second substance into thefirst substance; (d) a heating vessel for heating a mixture of the firstsubstance and the second substance; and (e) a radio frequency source ata suitable frequency and position for RF heating of the mixture.
 20. Thesystem of claim 19, further comprising a filter for filteringsubstantially all of the second substance comprising mini-dipolesusceptors from the first substance with a dielectric dissipationfactor, epsilon, less than 0.05 at 3000 MHz.